Electrocatalytic Hydrogen Evolution Research Articles

Improving electrocatalytic hydrogen evolution through Co and Ni single atom sites with synergistic effects anchored on carbon foam as a self-supporting electrode

Developing a new type of high-loaded single atom catalysts to further improve the performance of electrocatalytic hydrogen evolution reaction (HER) is still a major challenge. However, multiple single atom sites with synergistic effect between different atoms can promote catalytic activity. In this work, we develop a strategy based on inkjet printing-pyrolysis to anchor Co and Ni single atom sites on carbon foam substrate to form CoNi-N/CMF self-supporting electrode, which shows outstanding electrocatalytic hydrogen evolution performance. Aberration-corrected transmission electron microscopy revealed the coexistence of well dispersed Co and Ni single atoms with atomic distance of 5.3 Å, indicating part of Co and Ni single atoms are indirect bonding between the two atoms. CoNi-N/CMF showed impressive overpotential of 32.6 and 36.6 mV to reach a current density of 10 mA cm−2 under acidic and alkaline conditions, respectively, which is lower than that of Co or Ni single atoms. Density functional theory calculations revealed that the non-bonding configuration between the two metal atoms forms a synergistic effect to accelerate H* adsorption and desorption, thus optimizing the HER process. This paper provides a new method for the development of single atom catalysts.

Recent Modification Strategies of MoS2 towards Electrocatalytic Hydrogen Evolution

Hydrogen production by the electrolysis of water is a green and efficient method, which is of great significance for achieving sustainable development. Molybdenum disulfide (MoS2) is a promising electrocatalyst for hydrogen evolution reaction (HER) due to its high electrochemical activity, low cost, and abundant reserves. In comparison to the noble metal Pt, MoS2 has poorer hydrogen evolution performance in water electrolysis. Therefore, further modifications of MoS2 need to be developed aiming at improving its catalytic performance. The present work summarizes the modification strategies that have been developed in the past three years on hydrogen evolution from water electrolysis by utilizing MoS2 as the electrocatalyst and following the two aspects of internal and external modifications. The former includes the strategies of interlayer spacing, sulfur vacancy, phase transition, and element doping, while the latter includes the heterostructure and conductive substrate. If the current gap in this paper’s focus on modification strategies for electrocatalytic hydrogen evolution in water electrolysis is addressed, MoS2 will perform best in acidic or alkaline media. In addition to that, the present work also discusses the challenges and future development directions of MoS2 catalysts.

Heterostructured Pt-Ni3Mo3N formed via ammonia-containing polyoxometalates for highly efficient electrocatalytic hydrogen evolution in acid medium

Constructing heterostructured nanohybrid is considered as a prominent route to fabricate alternative electrocatalysts to commercial Pt/C for hydrogen evolution reaction (HER). In this work, (NH4)4[NiH6Mo6O24]·5H2O polyoxometalates (NiMo6) are adopted as the cluster precursors for simple fabrication of heterostructured Pt-Ni3Mo3N nanohybrids supported by carbon black (Pt-Ni3Mo3N/C) without using additional N sources. The improved porosity and enhanced electronic interaction of Pt-Ni3Mo3N/C should be attributed to the integration of Pt with NiMo6, which favors the mass transport, promotes the formation of exposed catalytic sites, and benefits the regulation of intrinsic activity. Thus, the as-obtained Pt-Ni3Mo3N/C exhibits impressive and durable HER performance as indicated by the low overpotential of 13.7 mV at the current density of 10 mA cm−2 and the stable overpotential during continuous working at 100 mA cm−2 for 100 h. This work provides significant insights for the synthesis of new highly active heterostructured electrocatalysts for renewable energy devices.

Electro-optical-magnetic-thermal coupling branched plasmonic heterojunction for efficient electrocatalytic hydrogen evolution and its dynamic process

Electrocatalytic hydrogen evolution reaction (HER) represents a potential technology to solve environmental and energy concerns. However, the high overpotentials and sluggish kinetics remain an essential challenge for electrocatalytic HER. Being different from the complicated strategies of electrocatalyst preparation, the present study focuses on a simple and feasible approach to improve electrocatalytic HER activity through a cooperative catalytic system. Here, we report a kind of multi-branched AgAuPt plasmonic heterojunction. Under the irradiation of 808 nm near-infrared (NIR) light, the localized surface plasmon resonance (LSPR) effect and the photothermal effect induce magnetic field and increased temperature, and achieve electro-optical-magnetic-thermal coupling in the catalysts. In addition, the dynamic process of the cooperative catalytic system is investigated as the temperature gradually changes. The proposed mechanism of the dynamic process is discussed in terms of the hopping rate of polarons (Kp). This work provides novel insights and inspirations into the design of cooperative catalytic system with improved electrocatalytic HER activity.

Strain engineering enhances electrocatalytic hydrogen evolution of B-N pair substituted biphenylene networks

The exploration of novel metal-free electrocatalysts with excellent activity and stability is important for scaling up hydrogen production via water splitting. Herein, we report a series of novel two-dimensional networks obtained by doping biphenylene (BPN) with B-N pairs, referred to as BCN-BPNs. Density functional theory calculations indicate that the designed BCN-BPNs are electronically and dynamically stable with metallic or semiconducting characteristics. It is further revealed that uniaxial lattice strain engineering is an effective approach to activating inert BPN and BCN-BPNs toward the hydrogen evolution reaction (HER). The best overpotential for HER is predicted to be 0.011 V, achieved by finely tuning strain. A machine learning model with an extreme gradient boosting regressor and a polynomial feature approach was successfully built to predict HER activities. The model achieved mean absolute errors and root mean squared errors of 0.068 and 0.261, respectively. Feature importance analysis highlights the role of both active sites and their microenvironment in determining HER activities. Our study suggests a series of novel metal-free BCN-BPNs with considerable potential for HER. Additionally, a predictive strategy is proposed for fast screening, which would benefit the development of HER catalysts that exhibit both cost-effectiveness and superior performance.

Preparation and Electrocatalytic Hydrogen Evolution Performance of FeCoNiCrMo High-Entropy Alloy Porous Electrode with Different Pore-Forming Agent Content

Preparation and Electrocatalytic Hydrogen Evolution Performance of FeCoNiCrMo High-Entropy Alloy Porous Electrode with Different Pore-Forming Agent Content

Preparation of Cu(OH)2/Cu2S arrays for enhanced hydrogen evolution reaction

AbstractCu(OH)2 has the advantages of ease of structural regulation, good conductivity, and relatively low cost, making it a suitable candidate material for use as an electrocatalyst. However, its catalytic efficiency and stability still need to be improved further. Therefore, Cu(OH)2/Cu2S was successfully prepared on copper foam (CF) using the in situ growth and hydrothermal method. The structural characterization showed that sulfidation treatment induced transformation of Cu(OH)2/CF from smooth nanorods into a coral‐like structure, which exposed more active sites of Cu(OH)2/Cu2S and enhanced the performance of electrocatalytic hydrogen evolution reaction (HER). Compared with Cu(OH)2, Cu(OH)2/Cu2S showed better alkaline HER performance, especially when the vulcanization concentration was 0.1 M, the overpotential of Cu(OH)2/Cu2S was 174 mV, and the reaction kinetics was 64 mv dec−1 at a current density of 10 mA cm−2. In this work, the morphology and electronic structure of copper‐based metal sulfide electrocatalysts were adjusted by sulfide treatment, which provided a new reference for improving HER performance.

Switch Volmer-Heyrovsky to Volmer-Tafel Pathway for Efficient Acidic Electrocatalytic Hydrogen Evolution by Correlating Pt Single Atoms with Clusters.

As cost-effective catalysts, platinum (Pt) single-atom catalysts (SACs) have attracted substantial attention. However, most studies indicate that Pt SACs in acidic hydrogen evolution reaction (HER) follow the slow Volmer-Heyrovsky (VH) mechanism instead of the fast kinetic Volmer-Tafel (VT) pathway. Here, this work propose that the VH mechanism in Pt SACs can be switched to the faster VT pathway for efficient HER by correlating Pt single atoms (SAs) with Pt clusters (Cs). Ourcalculations reveal that the correlation between Pt SAs and Cs significantly impacts the electronic structure of exposed Pt atoms, lowering the adsorption barrier for atomic hydrogen and enabling a faster VT mechanism. To validate these findings, this work purposely synthesize three catalysts: l-Pt@MoS2, m-Pt@MoS2 and h-Pt@MoS2 with low, moderate, and high Pt-loading, having different distributions of Pt SAs and Cs. The m-Pt@MoS2 catalyst with properly correlating Pt SAs and Cs exhibits outstanding performance with an overpotential of 47mV and Tafel slope of 32mV dec-1. Further analysis of the Tafel values confirms that the m-Pt@MoS2 sample indeed follows the VT reaction mechanism, aligning with the theoretical findings. This study offers a deep understanding of the synergistic mechanism, paving a way for designing novel-advanced catalysts.

Cr-Doped CeO2 Nanocrystals Supported on Reduced Graphene Oxide Nanosheets for Electrocatalytic Hydrogen Evolution

Cr-Doped CeO₂ Nanocrystals Supported on Reduced Graphene Oxide Nanosheets for Electrocatalytic Hydrogen Evolution

Interatomic interaction of 2D crumpled V2O5 nanosheets layered with Ni-MOF as a bifunctional electrocatalyst for overall water splitting and supercapacitor applications

Herein, we have synthesized a highly efficient and economical noble metal-free catalyst via a novel combination of V2O5 nanosheets and Ni MOF. The critical points of this study are (i) achieving a 2D layer structured crumpled V2O5 nanosheets without excessive stacking/aggregation using freeze drying method, (ii) decorating Ni-MOF over the crumpled V2O5 nanosheets to attain an excellent homogeneity and (iii) developing a V2O5 based novel and bifunctional electrocatalyst for overall water splitting and supercapacitor applications. Forming a well-interlinked morphological structure accompanies a homogeneous dispersion of Ni MOF over the V2O5 nanosheet. Among the multiple compositions, the NiV4 exhibited superior electrocatalytic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances with an overpotential (η30) of 336 mV and 108 mV, respectively. NiV4 also displayed remarkable stability as confirmed by chronopotentiometry (24 h) and CV (after 5000 cycles). The excellent OER performance is possible due to the interatomic interaction and the heterojunction formation between V2O5 nanosheets and Ni MOF, resulting in the preferential adsorption of ⁎OOH reaction intermediates to Ni active sites. During HER, the interfacial interaction between V2O5 nanosheets and Ni MOF allowed the OH− to adsorb on the V5+ center. Furthermore, the Ni active sites simultaneously accelerated the Volmer step by promoting the H adsorption. The uniform mass transfer routes aid in fast charge transfer, resulting in excellent OER and HER performances. Interestingly, in the 2-electrode system, the NiV4 exhibited an overpotential of 1.81 V at 10 mA cm−2 and excellent durability over 15 h. For supercapacitor applications, the NiV4 exhibits efficient specific capacitance (546 Fg−1 at 1Ag−1). Furthermore, the NiV4 electrode provides significant long-term stability during the supercapacitor application, with the stability being consistent after 10,000 cycles. The NiV4 offers excellent water splitting and supercapacitor performance due to its multifunctional properties and remarkable structural integrity.

Hydride-Containing Pt-doped Cu-rich Nanoclusters: Synthesis, Structure, and Electrocatalytic Hydrogen Evolution.

A structurally precise hydride-containing Pt-doped Cu-rich nanocluster [PtH2 Cu14 {S2 P(Oi Pr)2 }6 (CCPh)6 ] (1) has been synthesized. It consists of a bicapped icosahedral Cu14 cage that encapsulates a linear PtH2 unit. Upon the addition of two equivalents of CF3 COOH to 1, two hydrido clusters are isolated. These clusters are [PtHCu11 {S2 P(Oi Pr)2 }6 (CCPh)4 ] (2), which is a vertex-missing Cu11 cuboctahedron encaging a PtH moiety, and [PtH2 Cu11 {S2 P(Oi Pr)2 }6 (CCPh)3 ] (3), a distorted 3,3,4,4,4-pentacapped trigonal prismatic Cu11 cage enclosing a PtH2 unit. The electronic structure of 2, analyzed by Density Functional Theory, is a 2e superatom. The electrocatalytic activities of 1-3 for hydrogen evolution reaction (HER) were compared. Notably, Cluster 2 exhibited an exceptionally excellent HER activity within metal nanoclusters, with an onset potential of -0.03 V (at 10 mA cm-2 ), a Tafel slope of 39 mV dec-1 , and consistent HER activity throughout 3000 cycles in 0.5 M H2 SO4 . Our study suggests that the accessible central Pt site plays a crucial role in the remarkable HER activity and may provide valuable insights for establishing correlations between catalyst structure and HER activity.

Grain Boundary Tailors the Local Chemical Environment on Iridium Surface for Alkaline Electrocatalytic Hydrogen Evolution

AbstractEven though grain boundaries (GBs) have been previously employed to increase the number of active catalytic sites or tune the binding energies of reaction intermediates for promoting electrocatalytic reactions, the effect of GBs on the tailoring of the local chemical environment on the catalyst surface has not been clarified thus far. In this study, a GBs‐enriched iridium (GB−Ir) was synthesized and examined for the alkaline hydrogen evolution reaction (HER). Operando Raman spectroscopy and density functional theory (DFT) calculations revealed that a local acid‐like environment with H3O+ intermediates was created in the GBs region owing to the electron‐enriched surface Ir atoms at the GBs. The H3O+ intermediates lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the generation of hydrogen spillover from the sites at the GBs to the sites away from the GBs, thus synergistically enhancing the hydrogen evolution activity. Notably, the GB−Ir catalyst exhibited a high alkaline HER activity (10 mV @ 10 mA cm−2, 20 mV dec−1). We believe that our findings will promote further research on GBs and the surface science of electrochemical reactions.

Grain Boundary Tailors the Local Chemical Environment on Iridium Surface for Alkaline Electrocatalytic Hydrogen Evolution.

Even though grain boundaries (GBs) have been previously employed to increase the number of active catalytic sites or tune the binding energies of reaction intermediates for promoting electrocatalytic reactions, the effect of GBs on the tailoring of the local chemical environment on the catalyst surface has not been clarified thus far. In this study, a GBs-enriched iridium (GB-Ir) was synthesized and examined for the alkaline hydrogen evolution reaction (HER). Operando Raman spectroscopy and density functional theory (DFT) calculations revealed that a local acid-like environment with H3 O+ intermediates was created in the GBs region owing to the electron-enriched surface Ir atoms at the GBs. The H3 O+ intermediates lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the generation of hydrogen spillover from the sites at the GBs to the sites away from the GBs, thus synergistically enhancing the hydrogen evolution activity. Notably, the GB-Ir catalyst exhibited a high alkaline HER activity (10 mV @ 10 mA cm-2 , 20 mV dec-1 ). We believe that our findings will promote further research on GBs and the surface science of electrochemical reactions.

Modification 1T-MoS2 with surface ions towards electrocatalytic hydrogen evolution reaction

Molybdenum disulfide (MoS2) is considered as a thriving and cost-efficient electrocatalyst for hydrogen evolution reaction (HER). Unfortunately, the semiconductor phase of 2H-MoS2 itself has a conservative electronic intrinsic transport rate and the restricted active sites to edge regions, leading to unsatisfactory electrocatalytic performance of HER. Here, we have fabricated highly conductive metal phase 1T-MoS2 nanosheets by a hydrothermal method and introduced a series of transition metal ions on their surfaces by an in-situ reduction strategy to achieve MoS2 surface modification. It was found that the metals Ni and Co not only enhanced the intrinsic conductivity of 1T-MoS2, but also significantly increased the number of active sites in the catalyst, which resulted in the catalyst exhibiting excellent HER activity. Ni@1T-MoS2 exhibits fast reaction kinetics (86 mV·dec-1), good mechanical stability (~28 h) and low energy consumption in 1.0 M KOH medium, as well as an over-potential of only 187 mV at 50 mA·cm-2.

NiS/Ni3S4 decorated double-layered hollow carbon spheres for efficient electrochemical hydrogen evolution reaction and supercapacitor

NiS/Ni3S4 anchored on the double-layer hollow carbon spheres (DLHCs@NixSy) were rationally conceived and synthesized via calcination and hydrothermal process. A series of characterization results confirmed nickel sulfide consisted of NiS and Ni2S3 phases formed. Double-layer hollow carbon spheres as substrates with good electrical conductivity, high specific surface area and hollow structure, not only serve as the active sites for nickel sulfide targeting and electron conduction, but also adapt to the volume change on cycling. Sample DLHCs@NixSy-1:2 prepared using optimized conditions exhibited enhanced electrochemical performance and energy storage in electrocatalytic hydrogen evolution and supercapacitor, respectively. The hybrid nanostructure just needed to afford the potential of 263 mV to reach the current density of 10 mA cm−2 without IR correction and delivered a high specific capacitance of 1160 F g−1 at a current density of 1 A g−1. Encouragingly, the asymmetric supercapacitor device created using DLHCs@NixSy-1:2 and active carbon exhibited a high energy density of 40 Wh/kg at 375 W/kg within the voltage window of 0–1.5 V. Furthermore, the device revealed preeminent cycling performance with a retention rate of 70 % after 2000 cycles at 4 A g−1. This result provided a reference for the synthesis of dual-functional materials with low cost and high efficiency.

Insitu formation of low-valence state cobalt cation in octahedral sites of Co9S8 for highly efficient electrocatalytic hydrogen evolution

The elementary valence state in electrocatalysts has been demonstrated to significantly affect their catalytic ability. However, enhancing performance by controlling the elemental valence state and the precise doping location remains challenging. This work is devoted to exploring a controllable electronic structure that is capable of improving electrocatalytic hydrogen evolution activity by manipulating the valence state of an element at a specific location. This is demonstrated by reducing the high valence state Co3+ in octahedral sites of Co9S8 to form low valence state Co2+ using sodium borohydride. The occupation of Co2+ in the Co3+ site gives rise to the generation of local lattice distortion, which provides more efficient active sites for the hydrogen evolution reaction (HER). Additionally, Co2+ in octahedral sites donates more electrons to adsorbed water molecules, which facilitates HO–H dissociation and H∗ adsorption. The resulting electrocatalyst exhibits a low overpotential of 301 mV at 500 mA/cm2 for the HER, which is the best performance among all reported single-component Co9S8-based catalysts. This work paves an avenue for the rational design of HER electrocatalysts by precisely tuning the valence state of elements at specific locations.

Simultaneous control of crystallite size and interlayer spacing of MoS2 to achieve pseudocapacitive lithium intercalation

The functional properties of molybdenum disulfide (MoS2) are highly dependent on its structure. Here, we present a one-pot hydrothermal synthesis approach allowing to simultaneous control MoS2 structure over several length scales. Lowering the pH of the hydrothermal precursor solution leads to smaller crystallite sizes of the pristine MoS2 formed. Moreover, the addition of alkyldiamines to the same precursor solution leads to their physical confinement between the forming MoS2 layers without the formation of covalent bonds, yielding interlayer-expanded MoS2. Controlling alkyldiamine precursor concentration can vary the number of confined structural pillars in interlayer-expanded MoS2. Electrochemical lithium intercalation is tested as a function of MoS2 structural properties. It is revealed that both smaller crystallite sizes and expanded interlayer-spacing lead to an increasingly pseudocapacitive lithium intercalation signature. The number of lithium that is reversibly stored in interlayer-expanded MoS2 is increased to almost 1.5 per formula unit. The results provide a facile synthesis approach to simultaneously control MoS2 crystallite size and d-spacing, which may be of interest for applications beyond lithium intercalation, such as multivalent ion intercalation or electrocatalytic hydrogen evolution.

Fe−N bonds induced highly efficient Fe3O4/g-C3N4 heterojunction for electrocatalytic hydrogen evolution

Fe-based catalysts with the merits of the most abundant reserves in the crust, cheapest, and low toxicity, show significant superiorities to noble-metal catalysts for electrocatalytic water splitting. Fe3O4 as a member of Fe-based catalysts has been widely used for oxygen evolution reaction (OER). However, it is rarely applied for Hydrogen evolution reaction (HER) owing to the lack of inherent active sites for hydrogen absorption. Fe−N coordination bonds can act as active sites for electrocatalytic performance. Therefore, we reasonably designed and constructed Fe3O4/g-C3N4 heterojunction, where abundant Fe−N bonds acting as HER active sites were formed with the aid of rich Pyridine N of g-C3N4. Activity characterization result indicates the optimized 50%-Fe3O4/g-C3N4 heterojunction exhibits excellent HER performance with a low overpotential of 160 mV at 10 mA cm−2, a low Tafel slope of 77.18 mV dec−1, and outstanding cycle stability. Density functional theory (DFT) calculation demonstrates that the enhanced electrocatalytic performance stems from the Fe−N bonding interaction, which endows 50%-Fe3O4/g-C3N4 with lower water dissociation barrier and a moderate Gibbs free energy of hydrogen adsorption (ΔGH*) in comparison with pristine Fe3O4 and g-C3N4.

Ginkgo Leaf-Derived Carbon Supports for the Immobilization of Iron/Iron Phosphide Nanospheres for Electrocatalytic Hydrogen Evolution.

Iron/iron phosphide nanospheres supported on ginkgo leaf-derived carbon (Fe&FeP@gl-C) are prepared using a post-phosphidation approach, with varying amounts of iron (Fe). The activity of the catalysts in the hydrogen evolution reaction (HER) outperforms iron/iron carbide nanospheres supported on ginkgo leaf-derived carbon (Fe&FexC@gl-C), due to enhanced work function, electron transfer, and Volmer processes. The d-band centers of Fe&FeP@gl-C-15 move away from the Fermi level, lowering the H2 desorption energy and accelerating the Heyrovsky reaction. Density functional theory (DFT) calculations reveal that the hydrogen-binding free energy |ΔGH*| value is close to zero for the Fe&FeP@gl-C-15 catalyst, showing a good balance between Volmer and Heyrovsky processes. The Fe&FeP@gl-C-15 catalyst shows excellent hydrogen evolution performance in 0.5m H2SO4, driving a current density of 10mAcm-2 at an overpotential of 92mV. Notably, the Fe&FeP@gl-C-15 catalyst outperforms a 20wt% Pt/C catalyst, with a smaller overpotential required to drive a higher current density above 375mAcm-2.

Benzene-fused porphyrin(2.1.2.1) array: synthesis, structure, and electrocatalytic hydrogen evolution.

The development of efficient molecular catalysts for the electrocatalytic hydrogen evolution reaction (HER) is very necessary and important for fuel cells. In this work, we report a new benzene-fused porphyrin(2.1.2.1) array, BPD, with a unique S-shaped molecular conformation. The electrochemistry of BPD displays multielectron donating and accepting properties owing to the two porphyrin(2.1.2.1) blocks and degenerate molecular orbitals. The electrocatalytic HER activity of BPD is remarkably higher-that is, BPD exhibited lower overpotential, faster HER kinetics, faster charge transfer kinetics, and extended catalytic stability-than that of the porphyrin(2.1.2.1) copper complex monomer.